1. Field of the Invention
The present invention relates to an image forming apparatus such as an electrophotographic recording apparatus and a copying machine, a print process cartridge that is removably attached to an image forming apparatus, and a toner cartridge that is removably attached to a print process cartridge.
2. Description of the Related Art
One conventional electrophotographic recording apparatus is an electrophotography color image recording apparatus and incorporates a print medium transporting member and a plurality of image-forming sections. The print medium-transporting member transports a print medium to the image forming sections. The image forming sections are disposed in a direction in which the print medium is transported. The image-forming sections form toner images of corresponding colors. Each of the image forming sections has a print process cartridge, an exposing unit, and a transfer unit. The transfer unit transfers a toner image formed in the print process cartridge. The print process cartridge is removably attached to the image forming section. The print process cartridge includes a charging unit, a photoconductor, a developing unit, a cleaning unit, a toner cartridge, and a drive force-transmitting section. The drive force-transmitting section transmits a drive force for driving the charging unit, photoconductor, and developing unit. The charging unit charges the photoconductor. The exposing unit illuminates the charged surface of the photoconductor. Then, the exposing unit forms an electrostatic latent image on the surface of the photoconductor in accordance with print data. The developing unit applies toner to the electrostatic latent image on the photoconductor to develop the latent image into a toner image. The cleaning unit scratches off the toner that has failed to be transferred and remained on the photoconductor. The toner cartridge supplies toner to the developing unit. The toner cartridge is removably attached to the print process cartridge. The developing unit includes a developing roller and a toner-supplying roller. The developing roller is in pressure contact with the surface of the photoconductor. The developing roller applies the toner to the electrostatic latent image on the photoconductor to develop the electrostatic latent image into a toner image.
The toner cartridge includes an opening, an agitator, and a remaining-toner detecting mechanism, and holds toner therein. The toner is supplied through the opening from the toner cartridge to the toner supplying roller and developing roller. The toner-supplying roller supplies the toner to the developing roller. The agitator agitates the toner before supplying the toner to the developing unit. The agitator has an agitating shaft. The agitating shaft is linked to a remaining toner detecting mechanism. The remaining toner detecting mechanism detects an amount of the remaining toner from the operation of the agitator. A drive source rotates at a predetermined speed. The agitating shaft is supported by bearings. The agitating shaft rotates in such a way that the agitating shaft can be connected to and disconnected from the drive force transmitting section.
When the agitating shaft rotates, it is subject to a load of toner, which depends on an amount of remaining amount of toner. The time required for the agitating shaft to make one complete rotation depends on the load of toner. When the agitating shaft passes its top dead center, the agitating shaft drops due to its own weight toward the top surface of the pile of toner. When the amount of remaining toner is large, the agitating shaft falls through a short distance before it lands on the pile f toner. When the amount of remaining toner is small, the agitating shaft falls through a long distance before it lands on the pile of toner. The toner remaining detecting mechanism detects the amount of remaining toner by comparing the time required for the drive source to make one complete rotation with the time required for the agitating shaft to make one complete rotation.
A fine shaft is coupled to the agitating shaft and transmits the motion of the agitating shaft. The guide section constraints the motion of the tip portion of the sensor shaft to the reciprocating motion of the fine shaft. The toner cartridge is stored and is subject to mechanical vibration during transportation. Toner may be clumped in the toner cartridge due to mechanical vibration and long storage. Therefore, printing may be performed when a lump of toner is in the path of the tip portion of the sensor shaft. The toner cartridge allows the agitator to operate when printing is performed. The fine shaft operates to follow the motion of the agitator. The movement of the fine shaft is interfered with a lump of toner, so that the fine shaft is subject to a load due to the lump of toner. The bearing of the agitating shaft receives an increased load when the load on the fine shaft increases. When a load is exerted on the fine shaft, the rod may be deformed and sometimes may not regain its original shape. If the permanently deformed fine shaft is operated, the fine shaft may collide with surroundings or its mounting members.
Due to collision of the fine shaft with mounting members and the surroundings during the mounting operation, the fine shaft receives larger loads. The load on the fine shaft is transmitted to the agitating shaft. The load of the agitating shaft is transmitted to the drive source that drives the agitating shaft. Thus, an increased load may prevent the drive source from driving the agitating shaft normally.
If the agitating shaft cannot rotate normally, it cannot agitate the clumped toner normally. If the toner is not normally agitated, the toner cartridge cannot supply the toner normally to the developing unit. If a sufficient amount of toner is not supplied to the developing unit, an electrostatic latent image cannot be developed into a toner image normally. Because a toner image is no normally formed in the print process cartridge, the image forming sections fail to conduct normal printing.